MAINTAINERS: add samples/boards/google to Google platforms

Add the board samples path to Google platforms group so PRs there are
assigned.

Signed-off-by: Fabio Baltieri <[email protected]>

Author: fabiobaltieri

MAINTAINERS.yml

@@ -1545,6 +1545,7 @@ Google Platforms:
     - keith-zephyr
   files:
     - boards/*/google_*/
+    - samples/boards/google_*/
 
 Hash Utilities:
   status: maintained